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The number of alien species in the Mediterranean Sea is increasing rapidly, but few attempts have been made to evaluate impacts on specific habitat types. The present study investigated alien biodiversity in Mediterranean marine caves, both by contributing new records of Eastern Mediterranean cave aliens, and by reviewing the scattered existing literature; the main goals were to highlight potential impacts and investigate the importance of cave environments for the expansion of alien species. Seven new alien species were found in marine caves of the Aegean and Ionian seas, raising the total number of aliens reported from Mediterranean marine caves to 56 species, classified as molluscs, cnidarians, bryozoans, polychaetes, crustaceans, macroalgae, fishes and tunicates. Most cave aliens (66%) were recorded from the Southeastern Levantine coasts, specifically from Lebanese caves. Shipping and Lessepsian migration have been suggested as the main pathways of alien introduction into caves of the Mediterranean Sea. The comparison of alien cave biodiversity with the updated Mediterranean alien inventory (32 species added to the latest inventory) showed similar patterns and trends for species richness, biogeographical origin and major introduction pathways, corroborating previous findings on the high local representativeness of Mediterranean cave biodiversity. Alien species seem to have invaded mostly the entrance and semi‐dark zones of shallow and/or semi‐submerged caves and tunnels, whereas only a few have reached the dark inner sectors or caves of the anchialine type; thus, the unfavourable cave environment seems to be naturally protected from impacts related to opportunistic invasive species, at least to a certain point. Currently there is no research confirming any direct impacts of alien biota on the native cavernicolous one. However, some issues have emerged, implying potential threats that need to be further explored: (i) the presence of a considerable proportion of aliens in most studied marine caves of the Southeastern Mediterranean basin, (ii) the recently observed population explosion of alien cave‐dwelling fishes in the same area, (iii) several indications that alien diversity in marine caves is much higher than we know today. Quantitative surveys and monitoring schemes are needed in order to evaluate potential effects of alien diversity on cave community structure and the role of marine caves as stepping stones for its expansion in the Mediterranean.  相似文献   

3.
The common sole (Solea solea) is one of the most important demersal resources in the northern and central Adriatic Sea (GFCM GSA 17). Landings from this basin make up around 23% of the overall Mediterranean and Black Sea production. Despite the economic relevance of sole in the Adriatic Sea, and its inherent property of being shared among three countries (i.e. Italy, Slovenia and Croatia), studies on its spatial distribution are scarce and aged. Therefore, the aim of the present study was to assess the spatial distribution and investigate the dynamics of this species in the GSA 17. Samples of common sole were collected in the framework of yearly rapido trawl surveys (SoleMon), during late autumn, from 2005 to 2010, i.e. the spawning season of common sole in the Adriatic. Results highlighted that juveniles are mostly concentrated in shallow water (0–30 m depth) along the Italian coast and their spatial distribution persisted along the sampled years. By contrast adults were mainly distributed in the central/eastern part of the basin at depths > 30 m. As a result of the different spatial distributions, juveniles are exploited exclusively by Italian vessels, especially by beam trawlers (i.e. rapido trawl), while adults are caught by Croatian and Slovenian fishing fleets in their respective national waters and by the Italian fleet operating in international waters. These results, while shedding light on the common sole spatial ecology in the Adriatic, represent crucial information for the setting of international collaboration for a rational spatial-based management of the resource.  相似文献   

4.
The pleated ascidian Styela plicata (Lesueur, 1823) is a solitary species commonly found in ports and marinas around the world. It has been recorded in the Mediterranean region since the mid‐19th century. In the present work, the species’ genetic diversity was analysed, employing a 613‐bp portion of the mitochondrial cytochrome c oxidase subunit I (COI) gene from 149 individuals collected in 14 ports along Italian coasts at spatial scales ranging from 1 to approximately 2200 km. Haplotype and nucleotide diversity values were = 0–0.933 (total = 0.789) and π = 0–0.145 (total π = 0.0094), respectively. A general southward trend of increasing within‐population genetic diversity was observed. Analysis of molecular variance revealed significant genetic structuring but no significant differences were detected among basins, and no isolation by distance was found. Our data were integrated with the COI sequences available from previous studies and re‐analysed in order to investigate the possible routes of introduction of this ascidian into the Mediterranean Sea. The presence of the two COI haplogroups detected in previous molecular investigations on S. plicata at intercontinental spatial scale was confirmed in the Mediterranean Sea. The results revealed multiple introductions of S. plicata, although some locations appear to have experienced rapid expansion from few founding individuals with reduced genetic diversity. However, continuous introductions would confound the pattern deriving from single founder events and make it difficult to estimate the time needed for gene diffusion into established populations. This mixing of effects creates difficulties in understanding the past and current dynamics of this introduction, and managing this alien invasive ascidian whose genetic structure is continuously shuffled by vessel‐mediated transport.  相似文献   

5.
The Mediterranean endemic Cladocora caespitosa (Linnaeus, 1767) is a colonial scleractinian coral belonging to the family Faviidae and the only zooxanthellate coral from Mediterranean whose colonies may fuse in reef‐like structures (hermatypic). Recent surveys are focused on three locations where banks occur in the Adriatic Sea (Croatia): near Prvi? Island in the northern Adriatic, near Pag Island in the central Adriatic and in Veliko jezero (Mljet National Park) in the southern Adriatic. The C. caespitosa bank in Veliko jezero covers an area more than 650 m2 and is thus the largest bank of C. caespitosa found to date. The strong sea currents, which occur as a result of tidal exchange in the channel, appear to favour the growth of the bank. The goal of the study was to present the influence of major environmental factors upon the build‐up process of the coral bank. Biometrical parameters in the C. caespitosa colonies like diameter of the calyces, polyp ash free dry weight (AFDW), corallite linear growth rate and index of sphericity were investigated and compared from these three locations. The morphology of coral banks from the Adriatic Sea and the disposition of the biometrical values are affected by the sea currents, temperature and sedimentation.  相似文献   

6.
Hydroids are important components of the communities of rocky bottom shallow coastal areas. The hydrozoan fauna of the Mediterranean Sea is probably one of most investigated in the world, with lots of faunistic and biogeographical studies. However, quantitative studies using the same sampling methodology and controlled sampling effort have been restricted to areas in the Western and Central Mediterranean. We compared hydroid assemblages in four areas of the Mediterranean Sea, from the Gulf of Cádiz to the South Adriatic Sea, following the same sampling and quantification methodology. Our analysis showed the dominant Atlantic character of the assemblages of the Gulf of Cádiz and the South Alboran Sea because of the influence of the inflowing Atlantic waters. Conversely, the hydroid assemblages of the North Alboran Sea were more similar to the assemblages in the Ligurian and in the South Adriatic, and with a number of species ranking between the observed in these two Mediterranean zones. Fourteen species were identified as making the most significant contributions to characterizing the Mediterranean hydroid species pool from a quantitative point of view. These taxa include species previously named as typical components of the Mediterranean hydroid fauna as well as those only recently recorded in the region (Eudendrium moulouyensis) and invaders such as Clytia hummelincki.  相似文献   

7.
The Indo-Pacific oyster Chama pacifica Broderip, 1835 (Mollusca, Bivalvia, Chamidae) is rarely found in the Northern Red Sea reefs of Eilat (Gulf of Aqaba), where it is outnumbered by its indigenous congener, Chama savignyi Lamy, 1921. The influx of Eritrean biota from the Red Sea into the Mediterranean Sea via the Suez Canal has led to the formation of massive Chama oyster beds along the Eastern Mediterranean shore. However, unlike the Northern Red Sea, the Eastern Mediterranean Chama beds are dominated by C. pacifica oysters, whereas C. savignyi is absent from this region. In an attempt to understand this difference in their respective distribution, the reproductive biology of both species was compared. Histological analysis of the male and female gonads, monitored monthly from March 2009 to August 2010 in both regions, revealed a similar reproductive cycle, comprising six stages: onset of gametogenesis, advanced gametogenesis, ripe, ready to spawn, spent and sexual rest. Female gonads demonstrated an additional, seventh stage – restoration, coinciding with inferred spawning of ripe gametes. Both species were found to be dioecious spawners, with a single, annual, temperature-dependent inferred spawning period. Chama pacifica was found to reproduce efficiently in maximal Mediterranean seawater temperatures not experienced by the Northern Red Sea Chama populations. This study demonstrates the high invasive potential of an oyster species despite its rarity in its source region.  相似文献   

8.
The taxonomic richness and geographic distribution of sponges stranded along Sardinian shores were investigated in the long term by means of a revisited ancient sampling method in order to support a comprehensive species inventory. Almost all stranded species were Keratosa (n = 20), plus 6 species of other Demospongiae taxa. Dictyoceratida were dominant, with 6 genera and 19 species of the families Irciniidae, Spongiidae and Thorectidae: 9 Mediterranean endemics, 7 Atlanto‐Mediterranean and 3 widespread species. Regarding Dendroceratida, only the genus Spongionella was found. Some species (n = 8) were recorded for the first time in circum‐Sardinian seas. A high percentage (54.3%; 19 out of the 35 species) of the total Mediterranean Dictyoceratida fauna was recorded, including the most endangered Mediterranean species, that is of the genera Spongia and Hippospongia. Hippospongia communis, Ircinia variabilis, Spongia zimocca and Spongia officinalis were the most common species. Morphotraits of rare and/or poorly known species were investigated by scanning electron microscopy (SEM). Comparison among Sardinian sectors, and between Sardinian and adjacent seas, revealed a high similarity of stranded Dictyoceratida, despite the fact that the data from Tyrrhenian and Balearic–Catalan seas were collected mainly from SCUBA records. The cost‐effective sampling method used in the present study seems appropriate to the gross qualitative monitoring of coastal areas (e.g. large unexplored Northern African coasts), in order to assess the conservation status of Mediterranean Keratosa species. The wide distribution of all Mediterranean bath sponge species indicates their good conservation status in circum‐Sardinian seas, a datum that could usefully support the future management of this bioresource, particularly in protected areas.  相似文献   

9.
Temporal variability and population structure of planktonic ostracods were investigated for the first time in the South Adriatic Sea during 1996. The maximal total ostracod abundance (1167 ind·100 m−3; 69% juveniles, 18% females and 13% males) was recorded in February. Thirteen species of marine planktonic ostracods were identified. Porroecia spinirostris and Archiconchoecia striata dominated the ostracod assemblage, accounting respectively for 62% and 18% of the total abundance. Their annual peaks were recorded during the cold season, which was the period of their intense reproduction, with favourable temperature conditions and lack of predators. The females surpassed the males in abundance in most species. The presence of the mesopelagic species indicated a strong influence of intermediate layer water masses from the Eastern Mediterranean Sea.  相似文献   

10.
Gorgonians are important structuring species of the Mediterranean hard‐bottom communities that are threatened by disturbances such as increasing seawater temperature, mucilaginous events and destructive fishing, among others. In this study we assessed for the first time the population structure and conservation status of one of the most common gorgonians in the Eastern Adriatic Sea, the red gorgonian Paramuricea clavata. During late spring 2009, nine populations dwelling between 30 and 50 m depth were examined by SCUBA diving along 200 km of the Croatian coastline. The density ranged between 7 and 20 colonies·m?2. The mean and maximum colony heights were 31.2 ± 22.7 cm (±SD) and 138 cm, respectively. Two main patterns of P. clavata size frequency distributions were observed: the first one with a higher proportion of juveniles (~30%) observed mostly in the northernmost populations, and the second one with a higher proportion of larger colonies (>25% of colonies >40 cm in height). Regarding the disturbance impact level, the proportion of healthy colonies (with <10% of injured surface) was high in almost all of the studied populations (>60%) and the mean extent of injury (i.e. denuded axis or epibiosis) was 9.7 ± 4% (±SD), indicating low impacts. Contrasting population size structures with high recruitment in mature populations provides new insights into the demographic structure of the Mediterranean gorgonian forests dwelling in their upper bathymetric range (<50 m depth). Furthermore, these size structures and the low impact levels suggest a current favorable conservation status of the studied populations in the Eastern Adriatic Sea and provide a baseline for their monitoring in the future.  相似文献   

11.
The life cycle of the stoloniferan Cornularia cornucopiae (Pallas, 1766) (Anthozoa: Octocorallia) was studied from March 2009 to October 2010 on the rocky cliff of the Conero Promontory (North Adriatic Sea, 43°34.865′ N, 13°34.320′ E). In this area the species showed unusual high densities never recorded in other sites of the Mediterranean Sea. The density trend of the species showed a marked seasonal cycle, with a winter minimum of about 1000 polyps m?2 and a summer maximum of about 30,000 polyps m?2. In accordance with other Mediterranean literature data, polyps were fertile during spring–summer, from March to August, but the number of eggs per polyp continuously decreased during this span of time. Variations of polyp density were strongly correlated to water temperature, which can be considered the main environmental factor triggering this seasonal behaviour. The possibility, for C. cornucopiae, to face adverse winter conditions is probably related to the presence of a characteristic perisarcal envelope covering the stolon and the calyx of each polyp, which isolates the living tissues from the exterior. During winter, polyps degenerate but the stolons remain dormant inside their envelopes. The perisarc covering represents a morphological convergence of C. cornucopiae with benthic hydrozoans. As the latter, the studied stoloniferans are able to live in habitats characterized by periodic favourable conditions thanks to a seasonal life strategy. A similar trend is shared also by other important components (cnidarians and some sponges) of the filter‐feeding community of the North Adriatic Sea. Differently to the Western Mediterranean basin, this area is characterized by high food availability all year around, so benthic organisms are strongly constrained by the very low winter temperatures.  相似文献   

12.
Today, living banks of the coral Cladocora caespitosa appear to be restricted to a few Mediterranean locations and are threatened by the escalating impacts affecting coastal areas. In this study the exceptional occurrence of the Mediterranean coral C. caespitosa in the Columbretes Islands Marine Reserve (NW Mediterranean, Spain) is characterised in terms of spatial distribution, cover area, colony size and growth rates. The coral colonies form beds and banks in rocky bottoms within a semi‐enclosed bay that offers both hydrodynamic protection and high water exchange. The spatial distribution of the C. caespitosa colonies, from 5 to 27 m depth, is highly aggregated, depending on sea‐floor morphology and showing up to 80% of substrate coverage. The annual corallite growth rates obtained through the alizarin red staining method and x‐ray image analysis are similar, and range between 2.55 ± 0.79 mm and 2.54 ± 0.81 mm, respectively. The exceptional nature of these bioconstructions is due to their cumulative cover area, which is comparable in size to the largest C. caespitosa bioconstructions described to date in Mljet National Park (Croatia, Adriatic Sea).  相似文献   

13.
Abstract. In 1997, Artegiani et al. depicted for the first time the seasonal climatology of the Adriatic Sea; they used the ATOS data set, formed by 5540 oceanographic stations sampled over this continental basin from 1911 to 1980. Lately, two Italian institutes working on the Adriatic Sea for long time, IBM and IRPEM, merged their recent data sets for the northernmost part of the basin. This yielded 3600 new oceanographic stations, concentrated in an area where 809 ATOS stations were located. The new data were quality checked, and then a seasonal climatology was drawn up as a first analysis step. The new climatology differed significantly from the ATOS results; this could be explained, at least partially, by the climatic changes that have occurred on this area. For example, air temperature increased significantly over northern Italy starting from 1988. Variations of the observed air temperature and Po River runoff qualitatively agree with sea surface temperature and salinity variations. A preliminary computation of heat fluxes based on ECMWF reanalysis confirms an increased heat flux to the Northern Adriatic Sea starting from 1988.  相似文献   

14.
Canyons play a fundamental role in enhancing the abundance and diversity of marine organisms through the transport of organic matter and food resources, the presence of complex physical habitats and the absence of trawl fishing. During four baited lander deployments carried out in the Bari Canyon (Southern Adriatic Sea, Central Mediterranean), at depths of 443–788 m, about 43 h of video records were taken, for a total of 619,200 video frames. A total of 12 benthopelagic fish species (five chondrichthyes and seven osteichthyes) were identified. The blackspot seabream (Pagellus bogaraveo) was the most often observed fish species. The depth of 787 m represents a new depth record for this fish in the Adriatic Sea. Groups of up to 40 individuals of P. bogaraveo were attracted to the bait and were shown in single frames. The individuals were observed both exploring the area and feeding actively on the bait. The European conger (Conger conger) was recorded at each deployment. Clear scavenger behaviour was also observed in this teleost fish and in the shark Etmopterus spinax. The shark species Centrophorus granulosus and Hexanchus griseus, which are considered ‘vulnerable’ on the published IUCN Mediterranean Regional Red List, were also recorded but, although attracted by the bait, they were never seen feeding on it. Other fish species, harvested on fishing grounds, such as Merluccius merluccius, Helicolenus dactylopterus and Polyprion americanus, were also recorded. This study represents the first in situ documentation, at very low impact, of the fish fauna in the Bari Canyon, providing new insights into its small scale distribution and behaviour, the first in situ direct observation of the variable feeding behaviour of P. bogaraveo and its gregarious habits, as well as indicating that this canyon could act as a refuge area for species that are vulnerable to fishing on the open slope.  相似文献   

15.
X.H. Wang   《Ocean Modelling》2005,10(3-4):253-271
The Princeton Ocean Model was implemented to investigate the response of northern Adriatic Sea during the Bora event in January 2001 when strong wind and surface cooling was reported. The model has been run with realistic wind stress, surface heat flux and river runoffs forcings continuously from 1 January 1999 to 31 January 2001. The wind stress and surface heat flux was computed by the bulk parameterization, using the European Centre for Medium Range Weather Forecast analysis fields and the Comprehensive Ocean Atmosphere Data Set cloud data. All the freshwater sources along the Adriatic coastlines were represented by point or line source functions. Open boundary conditions in the Ionian Sea along a latitudinal boundary were nested within a large scale model of the Mediterranean Sea. The numerical study found that, before the Bora event of 13–17 January 2001, the water column of the northern Adriatic Sea was stratified by salinity, and the temperature was already cooler at the surface and over the shallower shelf region. The pre-Bora circulation of the northern Adriatic Sea was relatively weak and baroclinic with maximum surface currents occurred near the Italian coast. During the Bora event, the water column was well mixed in the most of coastal region of the northern Adriatic Sea. The atmospheric cooling produced colder water over the northern and western Adriatic Coast. The circulation of the northern Adriatic Sea was barotropic and dominantly wind driven, with maximum current speed of about 1 m s−1. The numerical study also demonstrated that the Bora event decreased the heat content of the water column with an area averaged value of 205 W m−2 over the shallow northern shelf. It was concluded that the heat budget of the northern Adriatic Sea during the Bora event was a balance between the surface heat loss, horizontal net heat inflow and resulting heat content decrease. The horizontal advection played a particularly important role in controlling the water temperature change over the shallower northern shelf.  相似文献   

16.
This study is the first to investigate and characterize the mycobiota associated with the alien species Asparagopsis taxiformis, a rhodophyte classified as one of the ‘100 worst invasive species’ in the Mediterranean Sea by the Hellenic Center for Marine Research, as it threatens biodiversity. Fungal endophyte and epiphyte communities were investigated on algal specimens from two sampling sites on the island of Linosa (Marine Protected Area Isole Pelagie, Italy). 87% of the 24 specimens that were analysed for epiphytes displayed a microfungal colonization. No endophytes were found. Only a small amount of microfungi was found to be associated with this alga. Only five fungal taxa were isolated; two of which are sporadically associated with the alga, while three, Eurotium rubrum, Cladosporium cladosporioides and Cladosporium pseudocladosporioides, seem to be related to A. taxiformis. This scarcity could be related to algal chemical composition.  相似文献   

17.
The population dynamics and gametogenesis of the non‐indigenous polychaete species Branchiomma luctuosum Grube, 1869 (Annelida, Sabellidae) has been investigated at three sites in the Taranto Seas (Ionian Sea, Mediterranean Sea). The species, probably introduced from the Red Sea, has been reported in the Mediterranean Sea since 1983. The species is hermaphrodite, and the reproductive season is between June and October when the largest mean size of oocytes was recorded together with the presence of mature spermatozoa. Small oocytes are present in specimens reaching about 20–25 mm in length. Therefore oogenesis seems to begin early during the first year of life, but the first reproduction can occur when the worms attain a larger size and are at least 6 months of age. Although most of the individuals reproduce seasonally within a discrete period, some individuals can reproduce in different periods during the year, the oogenesis of individuals not being synchronous. A life span of at least 2 years is highlighted, with a faster growth rate during the first months (about 20 mm per month) decreasing to about 10 mm from the 3rd to the 8th months and slowing down again after the worm reaches 100 mm in size. Some differences in growth performance are discussed, enhanced by comparing the sites located at greater depth (5–7 m) and those located at 0.5 m depth, together with the possible interactions of this alien species with the autochthonous sabellid Sabella spallanzanii.  相似文献   

18.
A quantitative model of the trophic network of Northern Adriatic Sea marine ecosystem during the 1990s has been constructed, with the goal of analysing its trophic structure, identifying the key trophic groups and assessing the anthropogenic impacts on the ecosystem using the Ecopath modelling protocol. The Northern Adriatic Sea is an eutrophic, shallow basin, and one of the most heavily fished areas in the Mediterranean Sea. The network aggregation into discrete trophic levels sensu Lindeman shows that low trophic levels dominate biomass and energy flows, with 40% of the total system throughput flowing out from trophic level 2. Instead, upper trophic levels appear bottom-up controlled, highly depleted and not exerting any control on the trophic network, as shown by mixed trophic impact-based analyses. Microbial loop is comparable to grazing with respect to the magnitude of flows involved, as 66% of the trophic network flows originate from detritus, which is mainly consumed by bacteria. Key trophic groups are plankton groups, macro-crustaceans and detritus, and other r-selected organisms like squids and small pelagics, which have a great influence on the ecosystem. In particular, zooplankton acts as a bottleneck for energy flows, limiting the energy from the low trophic levels effectively reaching the upper food web. The high pelagic production caused by eutrophication sustains high fishery landings and impressive discard quantities, as well as the benthic compartment. Overall, the ecosystem appears quite productive and in a stressed and developmental status. Model results and comparisons with few existing historical data suggest that the low maturity and stressed state of the Northern Adriatic Sea are not only due to natural characteristics, but mainly to anthropogenic pressures.  相似文献   

19.
The present study provides the first estimate of the daily ration for a goby species in the Mediterranean Sea, using a new approach to determine the mass of fish stomach contents through the sum of individual prey dry mass derived indirectly from prey size. Diel feeding activity and daily ration of the pelagic goby Aphia minuta were studied under natural conditions in the coastal waters off Comacchio (Northwestern Adriatic Sea) during the spring season. A total of 318 individuals of A. minuta, collected by 14 trawls carried out on 4 consecutive days, was examined for gut contents. The diel pattern of the vacuity index and the stomach fullness index indicated that A. minuta has nocturnal feeding behaviour. The daily ration, computed over a period of 16 h, was equivalent to 2.23% wet body mass.  相似文献   

20.
Abstract. An analysis was made of polychaete prey in the guts of 5 species of goatfishes ( Mullidiw): Upeneus usymmetricus , a Lessepsian migrant goatfish collected from both Mediterranean and Elat (Red Sea) locations; Mullus sunnuletus, ill. burbcuus , and U. moluccensis , a Lessepsian migrant taken only in the eastern Mediterranean; and Mulloides flavolineatus , collected in the Gulf of Elat. Mullus barbutus accounts for nine new polychaete records for the Mediterranean coast of Israel. Mulloides flavolineatus fed on two species which arc new records for the Gulf of Elat; one, Lumbrineris meteorunu , is a new record for the Red Sea. The polychaete prey provides some information on the ecology of the fishes: There appears to be little overlap regarding polychaete prey among the different goatfish species in the Mediterranean.  相似文献   

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